Single, multi-walled, functionalized and doped carbon nanotubes and composites thereof

ABSTRACT

The present invention relates to single walled and multi-walled carbon nanotubes (CNTs), functionalized CNTs and carbon nanotube composites with controlled properties, to a method for aerosol synthesis of single walled and multi-walled carbon nanotubes, functionalized CNTs and carbon nanotube composites with controlled properties from pre-made catalyst particles and a carbon source in the presence of reagents and additives, to functional, matrix and composite materials composed thereof and structures and devices fabricated from the same in continuous or batch CNT reactors. The present invention allows all or part of the processes of synthesis of CNTs, their purification, doping, functionalization, coating, mixing and deposition to be combined in one continuous procedure and in which the catalyst synthesis, the CNT synthesis, and their functionalization, doping, coating, mixing and deposition can be separately controlled.

1. BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to single walled and multi-walled carbonnanotubes (CNTs), functionalized carbon nanotubes and carbon nanotubecomposites with controlled properties, to a method for aerosol synthesisof single walled and multi-walled carbon nanotubes, functionalizedcarbon nanotubes and carbon nanotube composites with controlledproperties from pre-made catalyst particles and a carbon source in thepresence of reagents and additives, to functional, matrix and compositematerials composed thereof and structures and devices fabricated fromthe same in continuous or batch CNT reactors.

Description of Related Art

Carbon nanotubes are of great interest since they exhibit unique anduseful chemical and physical properties related to, for instance, theirmorphology, toughness, electrical and thermal conductivity and magneticproperties. Since their discovery, CNTs have been the subject ofintensive research and numerous patents, scientific articles and bookshave been devoted to their synthesis, properties and applications.Nanotubes were first observed during a direct-current arc dischargebetween graphite electrodes in an argon environment by Iijima (Nature1991, 354, 56). The typical temperatures for carbon nanotube productionby that method are about 2000-3000° C. Since then, various authorsdescribed alternative means of carbon nanotubes production, whichallowed increased production rate and significantly decreasedtemperatures, e.g., [Jiao and Seraphin, J. Phys. & Chem. Solids 2000,61, 1055; Hafner et al., Chem. Phys. Lett. 1998, 296, 195]. Forinstance, it has been shown that the presence of transition metalsdecreases the typical temperature required for tube production (e.g.,Jung et al., Diamond and Related Materials 2001, 10, 1235; Govindaraj etal., Materials Research Bulletin 1998, 33, 663; Shyu and Hong, Diamondand Related Materials 2001, 10, 1241). Since their discovery, severaldifferent production methods have been introduced to synthesize CNTs.These methods can be broadly divided into chemical and physicalaccording to the method applied in releasing carbon atoms fromcarbon-containing precursor molecules. In the physical methods, e.g.arc-discharge (Iijima, Nature 1991, 354, 56) and laser ablation (Guo etal., Chem. Phys. Lett. 1995, 243 49), high-energy input is used torelease the carbon atoms needed for tube synthesis. The chemical methodsrely on carbon atomization via catalytic decomposition of carbonprecursors on the surface of transition metal particles. According tothe place where the growth of CNTs occur, chemical methods for theirproduction can be divided into surface supported, so called CVD(chemical vapor deposition) [e.g. Dai et al., Chem. Phys. Lett. 1996,260, 471] and aerosol [e.g. Bladh, Falk, and Rohmund, Appl. Phys. A,2000, 70 317; Nasibulin et al., Carbon, 2003, 41, 2711] syntheses. InCVD methods, the carbon precursor decomposition and CNT formation takeplace on the surface of catalyst particles that are supported on asubstrate. In aerosol synthesis, the catalyst particles are in thegas-phase. The terms “gas-phase synthesis” and “floating catalystmethod” have been also applied in the literature for this process. Weuse the term “aerosol synthesis” to specify processes taking placecompletely in the gas-phase.

The method described in this patent is a new approach to the productionof single walled and multi-walled CNTs, functionalized CNTs and CNTcomposite materials and matrices thereof. This new method requirespre-made catalyst particles or a procedure to produce pre-made catalystparticles with a narrow distribution of properties, a carbon source, areagent, when needed, an energy source, when needed and a flow controlsystem. A principle advantage of the new method over existing methods isthat it allows the separate control of the introduction of catalystparticles and the CNT synthesis. In other methods, catalyst particlesare formed by gaseous chemical reactions leading to the formation ofsupersaturated vapor of the catalyst material (e.g. WO 00/26138) orphysical nucleation directly from supersaturated gas (e.g. WO 03/056078)simultaneously with the CNT synthesis and thus cannot be separatelycontrolled. This leads to the formation of CNTs with potentially largevariation in important properties such as length, diameter andchirality. The diameter and chirality of the CNTs produced via catalystsare largely determined by the properties of the catalyst particles, inparticular the catalyst size. Though patent US 2002/102193 A describes ameans of separately producing catalyst particles and CNTs, it does notspecify a means of controlling the high non-uniformity of catalystparticles produced by the chemical nucleation method proposed and thuswill tend to produce non-uniform CNTs. Our invention, on the other hand,provides a means of separately introducing catalyst particles with wellcontrolled properties, either directly though a process which inherentlyproduces catalysts with narrow particle size distributions (e.g. thephysical vapor nucleation processes described in this method), or byproviding specific means of narrowing the size distribution fromprocesses (such as the chemical nucleation method referred to in US2002/102193 A) which inherently produce wide catalyst particle sizedistributions and thus non-uniform CNTs. As the industrial andscientific utility of produced CNTs is a function of their individualand collective properties, there exists an urgent need for CNTs and amethod for production of CNTs and CNT composite formulations with moreuniform and controlled properties.

In our method we utilize pre-made particles for production of CNTs andCNT composite formulations. Those pre-made particles can be prepared byconventional methods such as chemical vapor decomposition of catalystprecursor [e.g. Nasibulin et al., J. Phys. Chem. B, 2001, 105, 11067.],by the physical vapor nucleation method, which implies an evaporationand subsequent vapor nucleation followed by growth of particles due tovapor condensation and cluster coagulation (for instance, a resistivelyheated hot wire generator, an adiabatic expansion in a nozzle or an arcdischarge method), by thermal decomposition of precursor solutiondroplets (e.g. by electrospray thermal decomposition) or by anyavailable method which either inherently produces particles with anarrow distribution of properties or can be pre-classified prior to CNTsynthesis to narrow the distribution. The pre-made particles are thenintroduced into a CNT reactor where CNT synthesis takes place. Thus, thecurrent invention separates the catalyst production from the CNTsynthesis and allows the control of each step in the production process.In order to produce CNTs with further controlled properties, thepre-made particles, either produced as part of the process or introducedfrom existing sources, can be classified according to size, mobility,morphology or other properties before being introduced into one or moreCNT reactors. Furthermore, the current invention allows the continuousor batch production of composite CNT either coated or mixed withadditive materials. Additionally, the current invention provides a meansof producing pure, functionalized or composite CNT gas, liquid or soliddispersions, solid structures, powders, pastes, colloidal suspensionsand surface depositions and can be integrated directly into a means offabricating structures from such materials. Additionally, when used inconjunction with the physical nucleation method, the current inventionprovides the additional advantage of allowing better control overconditions in the CNT reactor conditions since physical nucleationintroduces no additional chemical compounds into the environment whichcan interfere with CNT formation, growth, purification and/orfunctionalization.

2. SUMMARY OF THE INVENTION

The present invention relates to single walled and multi-walled carbonnanotubes (CNTs), functionalized carbon nanotubes and carbon nanotubecomposites with controlled properties, to a method for aerosol synthesisof single walled and multi-walled carbon nanotubes, functionalizedcarbon nanotubes and carbon nanotube composites with controlledproperties from pre-made catalyst particles and a carbon source in thepresence of zero or more reagents and zero or more additives, tofunctional, matrix and composite materials composed thereof andstructures and devices fabricated from the same in one or morecontinuous or batch CNT reactors. This method comprises the steps of:

-   -   (a) formation of catalyst particles (so-called pre-made        particles), if needed;    -   (b) size classification of the pre-made catalyst particles, if        needed;    -   (c) introducing the pre-made catalyst particles into the CNT        reactor;    -   (d) introducing one or more carbon sources into the CNT reactor;    -   (e) catalytic decomposition of one or more carbon sources;    -   (f) formation of CNTs;    -   (g) introducing zero or more reagents, which can be done        together with carbon sources or separately before, during or        after the CNT formation, to promote CNT formation, to purify        CNTs, to dope CNTs, and/or to functionalize the produced CNTs        when desired;    -   (h) introducing zero or more additives to the CNT aerosol to        produce a CNT composite material when desired;    -   (i) collection of produced CNTs and/or CNT formulations in a        solid, liquid or gas dispersion, a solid structure, a powder, a        paste, a colloidal suspension and/or as a surface deposition        when desired;    -   (j) deposition of gas dispersions of produced CNTs and/or        composite CNT formulations onto surfaces and/or into matrix        and/or layered structures and/or devices when desired.

The present invention includes one or more CNT reactors, which can allowcontinuous or batch production of CNTs, functionalized CNTs, doped CNTsand composites thereof. The present invention allows all or part of theprocesses of synthesis of CNTs, their purification, doping,functionalization, coating, mixing and deposition to be combined in onecontinuous procedure and in which the catalyst synthesis, the CNTsynthesis, and their functionalization, doping, coating, mixing anddeposition can be separately controlled. The present invention furtherprovides a composition of matter comprising single walled andmulti-walled CNTs and structures and devices fabricated from the same.

3. BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a block diagram of an arrangement for the method for CNTproduction.

FIG. 2 shows thermodynamic calculations of free Gibbs' energy ofdecompositions of example carbon sources at different temperatures.

FIG. 3 shows a preferred embodiment of the invention for CNT productionwhere the pre-made catalyst particles were formed by a physical vapornucleation method from a hot wire generator (a) separated in space fromthe CNT reactor and (b) smoothly integrated with the CNT reactor.

FIG. 4 shows CFD calculations of temperature contours in the vicinity ofa resistively heated wire (Inflow velocity U=1 m/s, T_(gas)=273 K,T_(wire)=1273K. Gravity points to the left).

FIG. 5 shows CFD calculations of (a) the temperature profile and (b)velocity vectors in a preferred embodiment of the invention. (Maximumwall T_(wall)=1273K, inner flow rate=0.4 LPM, outer flow rate=0.8 LPM.Gravity points to the left).

FIG. 6(a) shows an alternate embodiment of the invention for productionof single walled and multi-walled CNTs, where the pre-made catalystparticles are formed by decomposing one or more catalyst particleprecursors.

FIG. 6(b) shows an alternate embodiment of the invention for productionof single walled and multi-walled CNTs, where the pre-made catalystparticles are formed by a physical vapor nucleation method (forinstance, by an arc discharge) or by an electrospray thermaldecomposition method.

FIG. 6(c) shows an alternate embodiment of the invention for batchproduction of pre-made catalyst particles in combination with continuousproduction of single walled and multi-walled CNTs and CNT composites.

FIG. 6(d) shows an alternate embodiment of the invention for batchproduction of pre-made catalyst particles in combination batchproduction of single walled and multi-walled CNTs and CNT composites.

FIG. 6(e) shows an alternate embodiment of the invention for a singlebatch CNT reactor for production of pre-made catalyst particles andsingle walled and multi-walled CNTs and CNT composites.

FIG. 6(f) shows an alternate embodiment of the invention for continuousproduction of CNTs wherein sheath gas is used to insure catalystparticles and CNTs are not deposited on CNT reactor walls, thus avoidingsurface growth of CNTs and CNT composites.

FIG. 6(g) shows an alternate embodiment of the invention for continuousproduction of CNTs wherein a controlled temperature gradient in the CNTreactor is used to separate catalyst particle synthesis from CNTsynthesis.

FIG. 6(h) shows an alternate embodiment of the invention for productionof composite CNTs wherein an additional flow of coating material orparticles is introduced into the CNT aerosol flow and mixed to create acomposite formulation.

FIG. 6(i) shows a CFD calculation of an alternate embodiment of theinvention for production of CNTs and/or CNT composite formulationswherein controlled sampling of the product aerosol is used to isolate aportion of the aerosol flow that has experienced essentially uniformconditions as it has passed through the reactor(s) and/orpre-reactor(s).

FIG. 7 shows TEM images of single walled CNTs synthesized at 1200° C.from carbon monoxide as a carbon source using iron as a catalystmaterial.

FIG. 8 shows TEM and SEM images of multi-walled CNTs scratched from theCNT reactor walls.

FIG. 9(a) shows thermodynamic calculations of the temperature dependenceof mol fraction of the product after mixing 1 mol of CO and 1 mol of H₂.

FIG. 9(b) shows thermodynamic data for CO disproportionation:dependencies of free energy change, KG, and CO mol fraction in gaseousphase on temperature. Kinetic data: CO concentration afterdisproportionation on surface of nanometer iron particles.

FIG. 9(c) shows thermodynamic calculations of the temperature dependenceof the mol fraction of hydrogen atoms.

FIG. 9(d) shows thermodynamic temperature dependencies of the freeenergy change, □G, of reaction, leading to the liberation of carbon.

FIG. 10(a) shows number length distributions of CNTs produced at variousconditions.

FIG. 10(b) shows number diameter distributions of CNTs produced atvarious conditions.

FIG. 10(c) shows the correlation between diameters of catalyst particlesand produced CNTs.

FIG. 10(d) shows the dependence of the length of produced CNTs on the COflow rate.

FIG. 11 shows TEM images of single walled CNTs synthesized inside astainless steel tube at a set furnace temperature of 900° C.(t_(max)=1070° C.).

FIG. 12 shows TEM images of single walled CNTs synthesized at 1200° C.from carbon monoxide and ethanol/thiophene mixture as carbon sources andreagents using nickel as a catalyst material.

FIG. 13 shows TEM images of single walled CNTs synthesized at 1200° C.from ethanol as a carbon source and a reagent using iron as a catalystmaterial.

FIG. 14 shows TEM images of single walled CNTs synthesized at 1200° C.from ethanol/thiophene mixture as carbon sources and reagents using ironas a catalyst material.

FIG. 15 shows TEM images of multi-walled CNTs synthesized at 1200° C.from ethanol/thiophene mixture as carbon sources and reagents using ironas a catalyst material.

FIG. 16 shows TEM images of fullerene functionalized CNTs synthesized at900° C. from CO as carbon source and pure hydrogen as a reagent flowingthrough the hot wire generator using iron as a catalyst material andusing a stainless steel reactor tube.

FIG. 17 shows TEM images of fullerene functionalized CNTs synthesized at900° C. from CO as carbon source and water vapor as a reagent and usingiron as a catalyst material and using a stainless steel reactor tube.

4. DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to single walled and multi-walled carbonnanotubes (CNTs), functionalized carbon nanotubes and carbon nanotubecomposites with controlled properties, to a method for aerosol synthesisof single walled and multi-walled carbon nanotubes, functionalizedcarbon nanotubes and carbon nanotube composites with controlledproperties from pre-made catalyst particles and a carbon source in thepresence of zero or more reagents and zero or more additives, tofunctional, matrix and composite materials composed thereof andstructures and devices fabricated from the same in one or morecontinuous or batch CNT reactors. Once the CNTs are formed, they can bepurified, further functionalized and/or doped and/or further coated withadditional materials by, for instance, condensation of supersaturatedgas on the CNT surface or by being mixed with an additional aerosolsource, thus creating composite CNTs.

FIG. 1 shows a block diagram of an arrangement of the invention forsingle walled and multi-walled CNT production. The method can be acontinuous flow, batch or a combination of batch and continuoussub-processes. The first step of the method is to obtain aerosolizedpre-made catalyst particles. These particles can be produced as part ofthe process or can come from an existing source. Those particles can beclassified according to important properties (for instance, size, mass,shape, crystallinity, charge or mobility) or, when the distribution ofproperties is sufficiently narrow, can be directly introduced into theCNT reactor. In the CNT reactor, the pre-made catalyst particles aremixed and heated together with one or more carbon sources and with zeroor more reagents. Then, the carbon source catalytically decomposes.Reagents can be added into the CNT reactor for chemical reaction withcatalyst particles and/or carbon source and/or with CNTs. Thus, reagentscan be added together with one or more carbon sources, after thedecomposition of the carbon source, and/or after the CNT formation.During or after the formation of CNTs, the entire product or somesampled portion of the product can be selected for further processingsteps such as functionalization, purification, doping, coating andmixing. All or a sampled part of the resulting raw CNT product can thenbe collected directly, or incorporated into a functional productmaterial which can further be incorporated in devices.

Carbon Sources

According to the present invention, as a carbon source, various carboncontaining precursors can be used. Carbon sources include, but are notlimited to, gaseous carbon compounds such as methane, ethane, propane,ethylene, acetylene as well as liquid volatile carbon sources asbenzene, toluene, xylenes, trimethylbenzenes, methanol, ethanol, and/oroctanol. Alternatively and preferably, carbon monoxide gas alone or inthe presence of hydrogen can be used as a carbon source. Other carbonsources are possible and these examples are not intended to limit thescope of the invention in any way.

Thermodynamic calculations for decompositions of various carbon sourcesare presented in FIG. 2. This figure is provided to illustrate thevariety of possible desirable carbon sources and does not, in anyway,limit the sources for which the present method can be applied. Note thatincreasing the temperature in the system generally makes the potentialcarbon sources less stable, except for the reactions connected withcarbon monoxide: CO disproportionation and the reaction between CO andH₂. Those reactions will be discussed further as related to thedescription of the preferred embodiment and in Example 1.

For other carbon sources, increasing the number of atoms in saturatedhydrocarbons (CH₄, C₂H₆, C₃H₈) generally leads to a decrease in thestability of the substances. The stability behavior of systems withsaturated carbon bonds from C₂H₂ via C₂H₄ to C₂H₆ is more complex,because of its complex temperature dependency. Some liquid carbonsources are also included in this figure. One can see a trend foraromatic compounds (benzene C₆H₆, toluene C₆H₃—CH₃, o-xyleneC₆H₄—(CH₃)₂, 1,2,4-trimethylbenzene C₆H₃—(CH₃)₃). The most stable is thebenzene molecule. Increasing the amount of methyl groups in the compoundmakes compounds less stable. To control the properties of produced CNTs,such as chirality, fullerene molecules can be also used as a carbonsource. Nevertheless, all of the presented compounds and many othercarbon containing molecules can be used as a carbon source in thepresent invention. It is worth noting that the decomposition of carbonsources can occur even without the presence of catalyst particles, butbecause the decomposition is a kinetically limited process, a reasonabledecomposition rate at moderate temperatures and relatively low residencetimes can be obtained in the presence of catalyst particles.

Additionally, other methods can be used to activate carbon precursors atdesired locations in the reactors by using, for instance, heatedfilaments.

Catalyst Particles

As a catalyst material, various transition metals, which catalyze theprocess of carbon source decomposition/disproportionation known in theart can be used. A preferred catalyst particle consist of transitionmetals and combinations thereof, but other materials are possible.Generally preferred for CNT production are catalyst based on iron,cobalt, nickel, chromium, molybdenum, palladium. Other metal andnon-metal materials are possible according the invention and thepreceding examples are not intended to limit the scope of the inventionin any way.

The catalyst particles to be introduced into the CNT reactor can beproduced by various methods known in the art such as chemical vapordecomposition of catalyst precursor, physical vapor nucleation, or ofdroplets made by electrospray, ultrasonic atomization, air atomizationand the like or thermal drying and decomposition. Other methods forproducing catalyst particles are possible according to the invention andthe preceding list is in no way intended to limit the processesapplicable. Additionally, pre-made catalyst particles can be synthesizedin advance and then introduced into the CNT reactor, though, generally,particles of the size range needed for CNT production are difficult tohandle and store and thus it is preferable to produce them in thevicinity of the CNT reactor as an integrated step in the CNT andcomposite CNT production process.

For the chemical method of pre-made catalyst particle production,metalorganic, organometallic or inorganic compounds such as metallocene,carbonyl, and chelate compounds known in the art can be used as catalystprecursors. In general, however, due to the relatively slowdecomposition reaction for these precursors, relatively wide particlesize distributions are achieved with these methods, thus, to achieve thedesired control of catalyst particle sizes, these methods should be usedin conjunction with a pre-classifier. Other compounds are possibleaccording to the invention and these examples are in no way intended tolimit the compounds available according to the invention.

For the physical method of pre-made catalyst particle production, puremetals or their alloys can be evaporated by using various energy sourcessuch as resistive, conductive or radiative heating or chemical reaction(wherein the concentration of produced catalyst vapor is below the levelneeded for nucleation at the location of release) and subsequentlynucleated, condensed and coagulated from supersaturated vapor. Means ofcreating supersaturated vapor leading to the formation of catalystparticles in the physical method include gas cooling by convective,conductive and/or radiative heat transfer around, for instance, aresistively heated wire and/or adiabatic expansion in, for instance, anozzle. The hot wire method developed here, however, is preferable inthat it inherently produces catalyst particles with a narrow sizedistribution and thus does not require a pre-classification step toproduce CNTs with a narrow distribution of properties.

For the thermal decomposition method of pre-made catalyst particleproduction, inorganic salts can be used such as nitrates, carbonates,chlorides, fluorides of various metals. Other materials are possibleaccording to the present invention and these examples are not intendedto limit the scope of the invention in any way

In order stabilize the CNT production and to enhance the decompositionof carbon precursor at the catalyst particle surface, the reactor wallspreferably, but not necessary, should be saturated by the catalystmaterial. The wall saturation can be done by any available methods. Asan example, a chemical vapor deposition of the material on walls using acatalyst material compound as a precursor or by evaporation of catalystmaterial and allowing its condensation on the reactor walls can be done.Another possibility to have saturated conditions is to use a reactortube made of the catalyst containing material as is demonstrated inExample 3.

For the production of CNTs with further controlled properties, thepre-made particles can be classified according to, for instance,mobility or size and by, for instance, differential mobility analyzers(DMA) or mass spectrometers. Other methods and criteria forclassification are possible according to the present invention and thepreceding examples are not intended to limit the scope of the inventionin any way. Additionally, flow control, with, for instance, sheath gasand isokinetic sampling can be used to, for instance, provide uniformconditions for particle and CNT formation and growth and/or to classifyproduct according to reactor conditions so as to achieve for uniform CNTand composite CNT properties.

Promotion, Purification, Functionalization and Doping of CNTs

Reagents are needed for participation in the chemical reaction withcatalyst particle precursor and/or with catalyst particles and/or withcarbon source and/or with amorphous carbon and/or with CNTs. The purposeof the reagent is to be a promoter for the CNT formation and/or toincrease (or decrease) the rate of carbon source decomposition and/or toreact with amorphous carbon during or after the production of CNTs forpurification and/or to react with CNTs for functionalization and/ordoping of CNTs. The reagents can also behave as a carbon sourceaccording the present invention.

As a promoter for CNT formation, preferably sulfur, phosphorus ornitrogen elements or their compounds such as thiophene, PH₃, NH₃ can beused. Additional promoters include H₂O, CO₂ and NO. Other promotercompounds known in the art are possible according to the presentinvention and these examples are not intended to limit the scope of theinvention in any way.

Purification processes are generally needed to remove undesirableamorphous carbon coatings and/or catalyst particles encapsulated inCNTs. Usually this procedure takes significant time and energy, oftenmore than required for the CNT production itself. In the presentinvention it is possible to have one or more separated heated CNTreactors/reactor sections, where one CNT reactor or section of the CNTreactor is used to produce CNTs and the other(s) are used for, forinstance, purification, functionalization and/or doping. It is alsopossible to combine the growth and functionalization steps as shown inexamples 7 and 8. Amorphous carbon, deposited on the surface of CNTs,can be removed in one or more subsequent CNT reactors/reactor sectionsby, for instance, heat treatment and/or addition of special compoundswhich, for instance, form reactive radicals (for instance, OH), whichreact with undesirable products rather then with CNTs. One or moresubsequent CNT reactors/sections can be used for, for instance, theremoval of catalyst particles from the CNTs by creating the conditionswhere the catalyst particles evaporate as was shown in [Nasibulin etal., Carbon 2003, 412, 2711 and FI-20035120]. Other processing steps arepossible according to the present invention.

As a reagent for the reaction with a carbon source to alter itsdecomposition rate, hydrogen can be used. As an example, carbon monoxidereacts with hydrogen, namely, with hydrogen atoms, which are formed athigh temperatures due to decomposition of hydrogen molecules.

As a chemical for amorphous carbon removal, any compounds or theirderivatives or their decomposition products formed in situ in the CNTreactor, which preferably react with amorphous carbon rather then withgraphitized carbon, can be used. As an example of such reagents known inthe art, alcohols, ketones, organic and inorganic acids can be used.Additionally, oxidizing agents such at H₂O, CO₂ or NO can be used. Otherreagents are possible according to the present invention and theseexamples are not intended to limit the scope of the invention in anyway.

Another role of the reagent is to functionalize the CNTs. Chemicalgroups attached to CNTs alter the properties of the produced CNTs.Functionalization and doping of CNTs can radically change suchproperties as solubility and electronic structure (varying from wideband gap via zero-gap semiconductors to CNTs with metallic properties).As an example, the doping of CNTs by lithium, sodium, or potassiumelements leads to the change of the conductivity of CNTs, namely, toobtain CNTs possessing superconductive properties. Functionalization ofCNTs with fullerenes produces semi-conducting CNTs and allows furtherfunctionalization of the CNTs via the attached fullerenes by methodsknown in the art. In the current invention, the in-situfunctionalization and/or doping can be achieved via the introduction ofappropriate reagent before, during or after CNT formation.

Moreover, the reagent, which can be used for promotion, purification,functionalization, and/or doping of CNTs can be a carbon source as well.Also a carbon source, which can be used for the CNT production, can alsobe a reagent.

CNT Composites by Coating and Mixing

One or more additives can be used for coating and/or mixing with theproduced CNTs to create composite CNT formulations. The purpose of theadditives are to, for instance, increase the catalytic efficiency ofparticles deposited in a matrix or to control matrix properties of suchas hardness, stiffness and thermal and electrical conductivity orexpansion coefficient. As a coating or particle additive for CNTcomposite materials, preferably one or more metal containing or organicmaterials such as polymers or ceramics can be used. Other additivecompounds are possible according to the present invention and theseexamples are not intended to limit the scope of the invention in anyway. These can be deposited as a surface coating on the CNTs through,for instance, condensation of supersaturated vapor, chemical reactionwith previously deposited layers, doping agents or functional groups orby other means known in the art or, in the case that the additive is aparticle, mixed and agglomorated in the gas phase. Additionally, gas andparticle deposition on CNTs can be combined.

Classification

In order to produce CNTs with further controlled properties, pre-madeparticles, either produced as part of the process or introduced fromexisting sources, can be classified according to size, mobility,morphology or other properties before being introduced into the CNTreactor(s), where the CNT formation occurs. For instance, a highresolution differential mobility analyzer (HR-DMA) [Nasibulin et al., J.Nanoparticle Res. 2002, 4, 449], which allows a very high resolutionparticle size selection a with standard deviation of □≦1.025 at 1 nmparticle size, can be used as a classifier. Other examples include, butare not limited to, mass spectroscopy, sedimentation, diffusion,centrifugation, solvation, and chemical reaction according to theinvention. Additionally, controlling the flow field and temperaturedistribution in the reactor can be used as a means to control and/orclassify catalyst particle properties.

Energy Sources

Various energy sources can be used, when desired, to promote or impede,for instance, chemical reactions and CNT synthesis according to theinvention. Examples include, but are not limited to, resistively,conductively, radiatively or nuclear or chemical reactively heated CNTreactors and/or pre-reactors.

Controlled Sampling and Deposition of Aerosol Product

Various means can be used, when desired, to control or selectivelysample the CNT and composite CNT before and/or after functionalization,purification, coating, mixing and/or doping. Such control devices reducethe variation of product properties by selecting only those productsthat have been exposed to similar environmental conditions. Variousmeans of controlled sampling of the aerosol product are possibleaccording to the invention, including, but not limited to, selectivesampling from regions of the reactor with uniform conditions and aerosolfocusing through particle lenses, acoustic focusing devices, andelectrical focusing fields. Similarly, these techniques can be combinedby those experienced in the art to further enhance their controleffects.

Controlled deposition of synthesized materials can be achieved byvarious means including, but not limited to inertial impaction,thermophoresis and/or migration in an electrical field to form desiredgeometries (e.g. lines, dots or films) with desired properties such aselectrical or thermal conductivity, opacity or mechanical strength,hardness or ductility.

A method for producing single and multi-walled Carbon Nanotubes (CNT)sand composite CNTs from the gas phase comprising one or more CNTreactors; one or more sources supplying energy to said CNT reactor(s);one or more sources of pre-made aerosol catalyst particles introduced tosaid CNT reactor(s) wherein the catalyst particles are produced byphysical vapor nucleation of catalyst material or by solution dropletthermal decomposition of catalyst precursor or are aerosolized from apowder or suspension or wherein the catalyst particles are produced by achemical method and are subsequently pre-classified according to one ormore particle properties; one or more carbon sources introduced to saidCNT reactor(s).

A method additionally including one or more of: one or more pre-reactorsfor producing pre-made catalyst particles; one or more catalyst particleclassifiers; one or more CNT samplers; one or more CNT classifiers; oneor more sources supplying energy to said pre-reactor(s); one or morereagents supplied to said CNT reactor(s)/pre-reactors(s); one or moreaerosol samplers and/or classifiers extracting all or part of said CNTaerosol flow; one or more additives to said CNT reactor(s) and/orpre-reactors(s) to produce a composite CNT aerosol; one or more aerosolsamplers and/or classifiers extracting all or part of said composite CNTaerosol flow.

A method, wherein the catalyst precursor contains one or more metals.

A method, wherein the catalyst particles are formed due to thenucleation of supersaturated vapor wherein the vapor is evaporation fromone or more resistively heated wires consisting of one or more metals ormetal alloys, due to metal or alloy laser ablation, due to metal oralloy arc, spark or electrostatic discharge, due to evaporation from aconductively heated metal or alloy or due to evaporation fromradiatively heated metal or alloy.

A method, wherein the supersaturation is created by means of gas coolingby convective, conductive and/or radiative heat transfer and/oradiabatic expansion.

A method, wherein the catalyst precursor is a metalorganic,organometallic or inorganic catalyst containing compound.

A method, wherein the pre-made catalyst particles are classifiedaccording to one or more particle properties.

A method, wherein the pre-made catalyst particles are mobility-sizeclassified, mass classified, solubility classified, reactivityclassified, inertially classified, thermophoretically classified,diffusionally classified, charge classified, crystallinity classifiedand/or gravitationally classified.

A method, wherein the pre-made catalyst particles are classified by adifferential mobility analyzer or by a mass spectrometer.

A method, wherein the carbon source is an organic or inorganic carboncontaining compound.

A method, wherein the organic compound is a hydrocarbon.

A method, wherein the hydrocarbon is methane, ethane, propane,acetylene, ethylene, benzene, toluene, o-xylene, p-xylene,1,2,4-trimethylbenzene, 1,2,3-trimethylbenzene, C₁₅H₃₂, C₁₆H₃₄, C₁₇H₃₆,or C₁₈H₃₈.

A method, wherein the organic compound is an oxygen containing compound.

A method, wherein the oxygen containing compound is methanol, ethanol,propanol, butanol, pentanol, hexanol, heptanol, octanol, acetone, methylethyl ketone, formic acid or acetic acid.

A method, wherein the inorganic compound is carbon monoxide CO.

A method, wherein the residence time and/or temperature and/or catalystparticle properties and/or catalyst particle concentration and/orreagent concentration and/or carbon source concentration histories inone or more CNT reactors are controlled and the pre-made catalystparticles, carbon sources, reagents and carrier gases are continuouslyintroduced into the CNT reactor which is maintained at steady stateconditions and the products are continuously evacuated from the CNTreactor(s) and or pre-reactor(s) to comprise a continuous production ofproduct or the pre-made catalyst particles, carbon sources, reagents andcarrier gases are periodically introduced into the CNT reactor in whichthe conditions are controlled for a period of time and the products areperiodically evacuated from the CNT reactor(s) and or pre-reactor(s) tocomprise a batch production of product.

A method, wherein the reactor length, volume and/or wall temperatureand/or the flow rate of carbon sources and/or reagents and/or carriergases are used to control the residence time and/or temperature historyof catalyst particles and/or CNTs and/or composite CNTs in the CNTreactor(s) and or pre-reactor(s).

A method, wherein said CNT reactor(s) and/or pre-reactor(s) use sheathgas introduced through a porous or perforated wall, a co-flowing channelor an injection port to control the aerosol flow so as to minimizedeposition and/or to control the residence time, gaseous environmentand/or temperature history of catalyst particles and/or CNTs and/orcarbon nanotube composites inside the CNT reactor(s) and orpre-reactor(s).

A method, wherein said CNT aerosol sampler and/or composite CNT samplerselectively extracts a portion of carbon nanotubes and/or carbonnanotube composites from inside the CNT reactor(s).

A method, wherein said sampling is in the form of one or more isokineticsampling probes or one or more sampling probes combined with one or moreparticle aerodynamic lenses and/or one or more particle acoustic lenses.

A method, wherein the CNT reactor and/or pre-reactor surfaces containmaterial included in one or more catalyst particles or where the CNTreactor and/or pre-reactor surfaces are saturated with material includedin one or more catalyst particles.

A method, wherein the reagent(s) is/are used for participation in achemical reaction with one or more catalyst particle precursors and/orwith one or more pre-made particles and/or with one or more carbonsource and/or with amorphous carbon deposited on CNTs and/or with CNTs.

A method, wherein the chemical reaction of the reagent(s) with catalystparticle precursor and/or with pre-made particles is/are used forpromotion of CNT formation and/or where the chemical reaction of thereagent(s) with amorphous carbon is/are used for CNT purification and/orwhere the chemical reaction of the reagent(s) with the CNTs is/are usedfor CNT functionalization and/or CNT doping.

A method, wherein one or more reagents act also as a carbon source.

A method, wherein the reagent is an alcohol, H₂, H₂O, NO, CO₂, PH₃and/or NH₃.

A method, wherein the energy source is laser, electrical, resistive,conductive, radiative (in the entire range of the electromagneticspectrum) and/or acoustic heating, combustion or chemical reaction, ornuclear reaction.

A method, wherein the carrier gas and reagent gases entering thepre-reactor(s) are nitrogen and hydrogen and where the volume percent ofhydrogen is preferably between 0.1% and 25% and more preferably between1% and 15% and more preferably between 5% and 10% and most preferablyapproximately 7% and where there is one pre-reactor operated in serieswith one CNT reactor that is aligned with gravity and where thepre-reactor uses a hot wire generator to produce pre-made catalystparticles and where the hot wire generator has a wire diameter between0.01 and 10 mm and more preferably between 0.2 and 0.5 mm and morepreferably approximately 0.25 mm and where in the CNT reactor isessentially circular in cross section, oriented approximately verticallywith respect to gravity and has an inner diameter preferably between 0.5and 50 cm and more preferably between 1.5 and 3 cm and most preferablyapproximately 2.2 cm and a length preferably between 5 and 500 cm andmore preferably between 25 and 200 cm and most preferably approximately90 cm and where the CNT reactor wall is heated resistively.

A method, wherein the hot wire generator is separated in space from theCNT reactor and where in the carbon source is CO and where the CO isintroduced into the CNT reactor at a normalized volume flow rate ofpreferably between 5 and 5000 cm³/min and more preferably between 250and 800 cm³/min and most preferably at approximately 400 cm³/min andwhere the maximum CNT reactor wall temperature is between 600 and 15000degrees C. and more preferably between 850 and 5000 degrees C. and mostpreferably at approximately 1200 degrees C. and where in the flow ratethrough the pre-reactor is between 5 and 5000 cm³/min and morepreferably between 250 and 600 cm³/min and most preferably atapproximately 400 cm³/min and where the secondary and tertiary reagentsare thiophene and octanol and where the thiophene vapor pressure is mostpreferably between 1 and 1000 Pa and more preferably between 10 and 100Pa and more preferably between 20 and 40 Pa and most preferablyapproximately 30 Pa and where the octanol vapor pressure is mostpreferably between 0.1 and 100 Pa and more preferably between 1 and 10Pa and more preferably between 2 and 4 Pa and most preferablyapproximately 3.4 Pa.

A method, wherein the pre-reactor is essentially circular in crosssection, is smoothly integrated with the CNT reactor by inserted ittherein and aligning said pre-reactor with the centerline of said CNTreactor and where the hot wire generator is located essentially at theexit of the pre-reactor and where the end of the smoothly integratedpre-reactor is preferably located where the CNT reactor wall temperatureis between 0 and 5000 degrees C. and more preferably between 350 and 450degrees C. and most preferably approximately 400 degrees C. and wherethe inner diameter of the pre-reactor is preferrably between 0.1 and 5cm and more preferably between 0.5 and 1.5 cm and most preferablyapproximately 0.9 cm and where the outer diameter of the pre-reactor ispreferably between 0.2 and 10 cm and more preferably between 0.5 and 2.0cm and most preferably approximately 1.3 cm and where the maximum CNTreactor wall temperature is between 600 and 15000 degrees C. and morepreferably between 850 and 1500 degrees C.

A method, wherein the carbon source is CO and wherein the CO isintroduced into the CNT reactor around the pre-reactor at a normalizedvolume flow rate of preferably between 5 and 5000 cm³/min and morepreferably between 250 and 800 cm³/min.

A method, wherein the inner flow rate through the pre-reactor is between5 and 5000 cm³/min and more preferably between 250 and 600 cm³/min andmost preferably at approximately 400 cm³/min.

A method, wherein the CNT reactor walls are constructed from stainlesssteel.

A method, wherein the carbon source and a second reagent is ethanol andwherein the ethanol vapor pressure is preferably between 1 and 10000 Paand more preferably between 100 and 500 Pa and most preferably between150 and 300 Pa and most preferably approximately 213 Pa.

A method, wherein the carbon sources and secondary and tertiary reagentsare ethanol and thiophene and where the thiophene vapor pressure is mostpreferably between 0.01 and 1000 Pa and more preferably between 0.1 and30 Pa and more preferably between 0.2 and 15 Pa and where the ethanolvapor is pressure most preferably between 1 and 20000 Pa and morepreferably between 10 and 10000 Pa and more preferably between 50 and5000 Pa.

A method, wherein the reagent for the promotion of CNT growth andfunctionalization is hydrogen and wherein the volume percent of hydrogenin the hotwire generator is greater than 50% and more preferably greaterthan 90% and more preferably greater than 99%.

A method, wherein the reagent for the functionalization of carbonnanotubes is water vapor, wherein the water vapor is introduced in theouter CO flow via a saturator and where the concentration of water vaporis between 1 and 10000 ppm and more preferably between 10 ppm and 1000ppm and more preferably between 100 and 200 ppm and most preferablyapproximately 150 ppm.

A method, wherein there are two or more existing pre-made catalystparticle supplies which are composed of particles of essentially similarsizes, compositions, concentrations, states and/or morphologies or arecomposed of two or more distinct sizes, compositions, concentrations,states and/or morphologies.

A method, wherein there are two or more pre-reactors and saidpre-reactors are operated in parallel and said parallel pre-reactors areoperated at essentially similar conditions and/or with essentiallysimilar materials so as to produce pre-made catalyst particles ofessentially similar sizes, compositions, concentrations, states and/ormorphologies or said parallel pre-reactors are operated at differentconditions and/or with different materials and/or methods so as toproduce pre-made catalyst particles of two or more distinct sizes,compositions, concentrations, states and/or morphologies.

A method, wherein said CNT reactors are operated in parallel and saidparallel reactors are operated at essentially similar conditions and/orwith essentially similar materials so as to produce CNTs withessentially similar length, diameter, morphology and/or chirality orsaid parallel reactors are operated at different conditions and/or withdifferent materials and/or methods so as to produce CNTs with two ormore distinct lengths, diameters, morphologies and/or chiralities.

Carbon nanotubes prepared according to the above method.

Carbon nanotubes, wherein the length, diameter, number of walls,chirality, purity, and/or composition of dopants and/or attachedfunctional groups are controlled.

Functionalized carbon nanotubes, wherein the attached functional groupsare fullerenes, CNTs, transition metals, transmission metal oxides,polymers and/or polymer catalysts.

Carbon nanotubes, wherein the geometric standard deviation of the lengthis less than 2.5 or more preferably less than 1.5 or most preferablyless than approximately 1.25 and where in the geometric standarddeviation of the diameter is less than 2.5 or more preferably less than1.75 or most preferably less than approximately 1.4 and where thegeometric mean diameter is preferably between 0.4 and 25 nm and morepreferably between 0.75 and 5 nm and most preferably betweenapproximately 0.8 and 1.3 nm and where the geometric mean length ispreferably between 2 nm and 1 m and more preferably between 10 nm and1000 nm and more preferably between 25 nm and 100 nm and most preferablybetween approximately 45 and approximately 55 nm.

Carbon nanotubes, wherein the carbon nanotubes are coated with one ormore additive solids or liquids and/or solid or liquid particles toconstitute a carbon nanotube composite.

CNT composites, wherein one or more additive is introduced to the CNTreactor in the gas phase as a gas and/or as a liquid or solid aerosolparticle and/or wherein one or more additive gases are supersaturated soas to condense onto the CNT and/or wherein one or more additive gaseschemically react with the surface of the CNT and/or with anotheradditive, and/or with a functional group and/or with a doping materialof the CNT and/or wherein one or more additive aerosol particles areattached to the surface of the CNT to form a liquid, solid or mixedcoated CNT or a CNT-additive particle agglomerate or a mixture thereof.

Carbon nanotube composites, wherein the coating material is a metal, apolymer, an organic, a ceramic or a mixture thereof.

Carbon nanotubes and/or carbon nanotube composites, wherein the carbonnanotubes and/or composite carbon nanotubes are formulated as adispersion in a gas, a dispersion in a liquid, a dispersion in a solid,a powder, a paste or a colloidal suspension or are deposited on asurface.

A functional material made with above formulation.

A thick or thin film, a line, a wire or a layered structure composed ofabove functional material.

A thin or thick film, a line, a wire or a structure deposited byelectrical, acoustic, thermophoretic, inertial, diffusional,turbophoretic and/or gravitational forces.

A thin or thick film, a line, a wire or a structure, wherein thedeposition is enhanced by jet focusing.

A thin or thick film, a line, a wire or a structure, wherein the coatingmaterial is composed of one or more monomers and zero or more catalystsand the resulting functional material is heated so as to inducepolymerization.

A device made with any of the above materials.

A device, wherein the device is an electrode of a fuel cell or battery,a heat sink or heat spreader, a metal-matrix composite or polymer-matrixcomposite in a printed circuit or electron emitter in a field emissiondisplay.

5. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

FIG. 3(a) shows the preferred embodiment of the invention for thecontinuous production of single walled or multi-walled CNTs where thepre-made catalyst particles are formed by the physical vapor nucleationmethod from a hot wire generator (HWG) (3) separated in space from theCNT reactor. In said embodiment, a carbon source is supplied either froma carrier gas reservoir (1) (e.g. carbon monoxide, methane, ethane,etc.) or by a carrier gas passing through a saturator (6). The saturatorcan also be used to introduce reagents for e.g. CNT purification and/orfunctionalization. If the carbon source is a solid substance, it can beheated to increase the equilibrium vapor pressure. For liquidsubstances, the saturator can be, for instance, a bubbler. Roomtemperature is a suitable temperature to provide a suitable vaporpressure for some liquid carbon precursors (for instance, for methanol,ethanol, octanol, benzene, toluene, etc.). Nevertheless, the vaporpressure of the liquid substance can be adjusted by heating or coolingthe bubbler or by dilution.

Another carrier gas (pure nitrogen or nitrogen/hydrogen mixture, 93%/7%)is supplied from a carrier gas reservoir (2) to the HWG (3), which isoperated with the help of an electric power supply (4). As the carriergas passes over the heated wire, it is saturated by the wire materialvapor. After passing the hot region of the HWG, the vapor becomessupersaturated, which leads to the formation of pre-made particle due tothe vapor nucleation and subsequent vapor condensation and clustercoagulation. Inside the CNT reactor (5) or before, when needed, the twoseparate flows containing the pre-made catalyst particles and the carbonsource are mixed and subsequently heated to the CNT reactor temperature.The carbon source can be introduced through the HWG if it does not reactwith the wire. Other configurations are possible according to theinvention, so long as the catalyst particles are formed before CNTsynthesis begins.

It is known that nanoparticles posses very high diffusivity and highpinning energy with surfaces. In order to avoid diffusion losses of thecatalyst particles and to use them more efficiently, the distancebetween the HWG and the location where the formation of CNT occurs, canbe adjusted. FIG. 3(b) shows the equivalent embodiment when the pre-madecatalyst particles are formed by a physical vapor nucleation method froma hot wire generator smoothly integrated with the CNT reactor. Here, theHWG is located inside the first section of the CNT reactor. In thispreferred embodiment, the end of the HWG tube was placed at the locationwhere the CNT reactor wall temperature of about 400° C. This temperaturewas found to be optimal, since reduced particle growth due to thecatalyst particle agglomeration and coagulation, minimized particlediffusion losses on the walls and provided a reasonable iron vapornucleation rate.

The metal particle size is of great importance in the formation of CNTssince CNT diameter has been shown to correlate with catalyst particlesize. The nucleation rate and final particle size depend on thetemperature gradient over the metal wire and on the concentration of themetal vapor. The concentration of the vapor and the temperature gradienton the other hand depend on the gas flow rate over the metal wire andthe wire temperature. Since large temperature gradients (≈500000 K/s)can be achieved, the HWG can be applied to the production of very smallprimary particles. The temperature change over the heated metal wire wascalculated with a Computational Fluid Dynamics (CFD) model. In thecalculation, an incoming gas velocity (U) of 1 m/s and temperature of273 K were used. As can be seen in FIG. 4, the temperature gradient nearthe wire surface is extremely large meaning that the metal vapor rapidlycools down (approximately 500° C. in 1 mm distance). Correspondingly,the vapor reaches supersaturation very quickly, which in turn results inhomogeneous nucleation of large number of small metal clusters.Calculations show that the temperature drops such that homogenousnucleation of catalyst particles should be complete with a fewmillimeters of the hotwire. Furthermore, it has been found that themethod produces exceptionally narrow particle size distributions and socan be used in the current invention without the necessity of a particleclassification step as would be needed in, for instance, typicalchemical nucleation methods.

CFD calculations were carried out to define the temperature and velocityprofiles and mixing conditions in the CNT reactor (namely, in thepreferred embodiment shown in FIG. 3(b)) under laminar conditionsincluding the effects of buoyancy. Results of the CFD calculations areshown in FIG. 5(a) and FIG. 5(b) and exhibit how the current inventioncan be constructed to define the residence time and temperature historyof carrier gases and reagents, catalyst particles and carbon nanotubesin the CNT reactor so as to control catalyst particle and nanotubegrowth.

6. DESCRIPTION OF SAMPLE ALTERNATE EMBODIMENTS

FIG. 6(a) shows another embodiment used, according to the presentinvention, for the production of the single walled and multi-walledCNTs. In this figure, the system for production of pre-made catalystparticles consist of a carrier gas cylinder (2), saturator (8) and (6),a pre-reactor (7) and a particle classifier (9). It should be noted thatthe carrier gas can be a carbon source as well. The saturator (8) can beused for the carrier gas saturation by a carbon source. The saturator(6) can be used for the carrier gas saturation by a catalyst precursor.Saturators (6) and (8) can also be used to introduce reagents into thesystem for, for instance, CNT purification or functionalization. If thecatalyst precursor and carbon source are solid substances, they can beheated to increase their equilibrium vapor pressures. For liquidsubstances, the saturator can be, for instance, a bubbler. Roomtemperature is a suitable temperature for a necessary vapor pressure ofsome liquid catalyst precursors (for instance, for iron pentacarbonyl)and carbon sources (for instance, benzene and toluene). Nevertheless,the vapor pressure of the liquid substance can be adjusted by heating orcooling the bubbler. Another possibility to decrease the vapor pressureof the liquid after the bubbler is to dilute the liquid with a suitablesolvent or to dilute the vapor with an inert gas. For instance, amixture of benzene and cobalt carbonyl can be used to decrease the vaporpressure of Co(CO)₄. Moreover, one or more furnaces or furnace sectionscan be used. Zero or more furnaces/furnace sections can be used forcatalyst production and one or more furnaces/furnace sections can beused for CNT formation. Additional furnaces/furnace sections can be usedfor purification and/or functionalization and/or doping of CNTs. Zero ormore reagents can be added in the system before, during and/or after CNTformation.

The pre-reactor (7) and/or CNT reactor (5) can be, but are notnecessarily, resistively heated. Other energy sources can be applied toenergize and decompose the precursor. For instance, it can beradio-frequency, microwave, acoustic, laser induction heating or someother energy source such as chemical reaction.

The formed pre-made catalyst particles can be classified in size in aparticle classifier (9). For this purpose, a differential mobilityanalyzer can be used. Other criteria and methods can, according to theinvention, be used for classification. Subsequently, the pre-madeparticles are introduced into the CNT reactor.

A sample alternate embodiment of the invention for continuous singlewalled and multi-walled CNT production where the pre-made catalystparticles are made by the physical vapor nucleation method (forinstance, adiabatic expansion in a nozzle or an arc discharge) or bythermal decomposition of precursor solution droplets is shown in FIG.6(b). All the elements remain the same as in the previous samplealternate embodiment except that, instead of the saturator (8) and thepre-reactor (7) (in FIG. 6(a)), another system for the production of thepre-made particles (10). Box (10) depicts, for example, adiabaticexpansion in a nozzle, an arc discharge or electrospray system for theformation of metal containing particles. Other methods are applicableaccording to the invention and these examples are not intended to limitthe scope of the invention in any way. Box (10) can also represent ameans of aerosolizing pre-existing catalyst particles. The aerosolpre-made particles can be classified in a classifier (9) or introduceddirectly to the CNT reactor (5). Methods involving chemical nucleationwill, in general, require pre-classification to achieve the desireduniformity in particle properties for well controlled CNT production.

A sample alternate embodiment of the invention for batch production ofpre-made particles and continuous production of single walled andmulti-walled CNT production is shown in FIG. 6(c). As in the continuousprocesses, the pre-made particles can be prepared by any of thedescribed methods such as physical nucleation, chemical vapordecomposition, or electrospray thermal decomposition in one or morebatch CNT reactors (11) by introducing one or more carriers, catalystprecursors, carbon sources and/or reagents through one or moreinlet(s)/outlet(s) (12) and subsequently evacuated after the batchprocess is completed though inlet(s)/outlet(s) (12). Alternately,pre-made catalyst particles can be directly introduced into the CNTreactor(s) or first classified in the classifier (9).

A sample alternate embodiment of the invention for batch production ofpre-made particles and batch production of single walled andmulti-walled CNT production is shown in FIG. 6(d). As in the continuousprocesses, the pre-made particles can be prepared by any method such asphysical nucleation, chemical vapor decomposition, or electrospraythermal decomposition in one or more batch CNT reactors (11) byintroducing one or more carriers, catalyst precursors, carbon sourcesand/or reagents through one or more inlet(s)/outlet(s) (12) andsubsequently evacuated after the batch process is completed thoughinlet(s)/outlet(s) (12). Alternately, pre-made catalyst particles can bedirectly introduced into the CNT reactor(s). Once these particles areproduced, they can be introduced into the CNT reactor (13) through oneor more inlet(s)/outlet(s) (14) where the time, gas composition andtemperature history can be adjusted for CNT growth. Subsequently, theCNT reactor can be evacuated though inlet(s)/outlet(s) (14) and the CNTscollected.

FIG. 6(e) depicts a sample embodiment wherein only one batch CNT reactoris used for both production of pre-made catalyst particles and for CNTsynthesis. As in the previous embodiments, the pre-made particles can beprepared by method such as physical nucleation, chemical vapordecomposition, or electrospray thermal decomposition in a batch CNTreactor (13) by introducing precursors, reagents and/or carrier gasesthrough one or more inlet(s)/outlet(s) (14). Alternately, pre-madecatalyst particles can be directly introduced into the CNT reactor(s).Once the batch process is complete, appropriate carriers, catalystprecursors, carbon sources and/or reagents are introduced into the CNTreactor (13) through one or more inlet(s)/outlet(s) (14) where the time,gas composition and temperature history can be adjusted for CNT growth.Subsequently, the CNT reactor can be evacuated though inlet(s)/outlet(s)(14) and the CNTs collected.

FIG. 6(f) depicts a sample embodiment wherein sheath gas is used tocontrol the catalyst particle and CNT deposition and heating in the CNTreactor tube in the case of a continuous flow system. Here a furnace(17) heats one or more carriers, catalyst particles, catalystprecursors, carbon sources and/or reagents introduced through inlet(18). Additional sheath gases are fed to the CNT reactor through one ormore porous tubes (21), thus insuring the CNT reactor surfaces are freeof catalyst particles and CNTs. Said sheath flow(s) can consist of oneor more carriers, catalyst precursors, carbon sources and/or reagentsaccording to the invention. The resulting aerosol then exits the CNTreactor through outlet (19). Other methods of flow control to minimizecatalyst particle and CNT deposition are possible according to theinvention.

FIG. 6(g) depicts a sample embodiment wherein a single furnace with agradually increasing wall temperature is used to separate the catalystparticle production from the CNT formation. In this embodiment, acontinuous flow CNT reactor is divided into multiple temperature heatingblocks (22) and (23). All required carrier gases, catalyst precursors,carbon sources and/or reagents are introduced though inlet (18). Thetemperature of heating block (18) is set high enough such that thecatalyst particle precursor decomposes to produce catalyst particles bya chemical nucleation method but below that needed to initiate CNTsynthesis. The temperature of heating block (22) is set above thatneeded to initiate CNT synthesis. Each block of the CNT reactor can thenbe controlled independently thus creating two distinct CNT reactorsections smoothly integrated with one another. Other methods ofseparating the catalyst particle synthesis and CNT synthesis in acontinuous or batch production process are possible according to theinvention.

FIG. 6(h) depicts a sample embodiment of the invention for continuousproduction of CNT composites wherein an additional flow of additivecoating material or aerosolized particles (24) is introduced into theCNT aerosol flow (25) to create a composite material. Examples ofpossible additives include, but are not limited to, polymers, metals,solvents and ceramics and aerosols thereof. The resulting compositeaerosol (26) can then be directly collected, deposited in a matrix ordeposited on a surface by electrical, thermophoretic, inertial,diffusional, turbophoretic, gravitational or other forces known to theart to form thick or thin films, lines, structures and/or layeredmaterials. Further control can be achieved by, for instance, jetfocusing of the resulting CNT aerosol stream.

FIG. 6(i) shows a CFD calculation of an alternate embodiment of theinvention for production of CNTs and/or CNT composite materials whereincontrolled sampling of the product aerosol is used to isolate a portionof the aerosol flow that has experienced essentially uniform conditionsnear the reactor centerline throughout the reactor(s) and/orpre-reactor(s). Other means of controlled sampling of the aerosolproduct are possible according to the invention, including, but notlimited to, aerosol focusing through particle lenses, acoustic focusingdevices, and electrical focusing fields.

7. EXAMPLES

In order to facilitate a more complete understanding of the invention,examples are provided below. These examples are for purposes ofillustration only and are not intended to limit the scope of theinvention in any way.

In all the following examples, the morphology and the size of theproduct are investigated with a field emission transmission electronmicroscope (TEM, Philips CM200 FEG) and a field emission scanningelectron microscope (Leo Gemini DSM982). Electron diffraction (ED)patterns of the products were used for determination of the crystallinephase of metal particles.

Where various embodiments of the present invention are described indetail, it is apparent that modifications and adaptations of thoseembodiments will occur to those skilled in the art. However, it is to beexpressly understood that such modifications and adaptations are withinthe spirit and scope of the present invention.

Example 1 Single Walled CNT Synthesis from Carbon Monoxide as CarbonSource Using Iron as Catalyst Material and Using a Ceramic Reactor Tube

Carbon source: CO.

Catalyst particle source: hot wire generator.

Catalyst material: iron wire of 0.25 mm in diameter.

Operating furnace temperature: 1200° C.

Operating flow rates: CO outer flow of 400 cm³/min and hydrogen/nitrogen(7/93) inner flow of 400 cm³/min.

This example, illustrating the synthesis of single walled CNTs, wascarried out in the embodiment of the invention shown in FIG. 3(b).Carbon monoxide was supplied from a gas cylinder (1) and theexperimental setup did not contain a saturator (6). The embodimentconsisted of a HWG smoothly integrated with a heated vertical tubularCNT reactor. A ceramic tube, with an internal diameter of 22 mm insertedinside the 90-cm length furnace (Entech, Sweden) was used as a CNTreactor. Inside the CNT reactor another ceramic tube with external andinternal diameters of 13 and 9 mm, respectively and with a length of 25cm was inserted. The HWG, which was a resistively heated thin iron wire,was located inside the internal tube. The location of the internal tubecould be adjusted. The end of the HWG tube was placed at the locationwith the CNT reactor wall temperature of about 400° C. This temperaturewas found to be optimal, since reduced particle growth due to theagglomeration and coagulation, minimized particle diffusion losses onthe walls and provided a reasonable iron vapor nucleation rate.

In order to suppress the iron particle evaporation inside the reactor,the walls of the reactor tube were saturated with iron by running HWG innitrogen/hydrogen atmosphere without carbon monoxide. Also it ispossible to saturate the reactor walls by blowing iron containingcompound vapor through the heated up to about 1000° C. reactor. For thispurpose, the vapor of ferrocene or iron pentacarbonyl can be used.

The metal particles produced by the HWG were carried into the CNTreactor with nitrogen/hydrogen (with mol component ratio of 93.0/7.0)from gas cylinder (2) shown in FIG. 3(b). In the CNT reactor, the flowof the metal particles from the HWG was mixed with the outer CO flow.Inside the CNT reactor CO disproportionation or hydrogenation took placeon the surface of the formed metal particles. Downstream of the CNTreactor a porous tube dilutor (12 L/min) was used to prevent the productdeposition on the walls. The aerosol product was collected by anelectrostatic precipitator (Combination electrostatic precipitator,InTox Products) on a carbon coated copper grid (SPI Lacey Carbon Grid).FIG. 7 demonstrates the product formed at the given operatingconditions. CNTs are single walled. The number diameter and lengthdistributions obtained on the basis of high-resolution TEM images arepresented in Example 2. An important characteristic of this process isthe efficiency of the catalyst material usage. Almost all catalystparticles initiated the growth of CNTs.

During the experiments also multiwalled CNTs (MWCNTs) were produced onthe wall of the CNT reactor. Scratching the product from the wallsupstream of the CNT reactor at about 700° C. (after a 10 hourexperiment) showed the presence of well crystalline MWCNTs among theproduct (FIG. 8). The MWCNTs are shown to be a few microns long. TEMobservations showed that the product consisted of different types ofCNTs: bamboo-shaped tubes, MWCNTs with either a small (about 5) or alarge (up to 50) number of walls. Scratching the product from the wallsafter one week of operation showed very thick carbon tubes of about 200nm in diameter. Thus, it is demonstrated that CNTs produced in theaerosol phase are markedly different from surface supported (i.e. CVD)produced CNTs.

Thermodynamic Calculations

It is well known that at the studied furnace temperatures, two competingreactions, CO disproportionation and hydrogenation, leading to theformation of CNTs can occur. Since there were no CNT produced in theabsence of hydrogen, we assume that the hydrogenation reaction of carbonmonoxideH_(2(g))+CO_((g))

C_((s))+H₂O_((g)), □H=−135 kJ/mol   (1)plays a very important role. The justification of the occurrence of thisreaction can be seen from the thermodynamic calculations presented inFIG. 9 (a). It is worth noting that the concentration of the releasedcarbon after reaction (1) is proportional to the concentration of water.Thus, reaction (1) can occur at temperatures lower than 900° C., whileat the temperatures higher than that, the reaction is prohibited. It isnecessary to note that this behavior is similar to the reaction of COdisproportionationCO_((g))+CO_((g))

C_((s))+CO_(2(g)), □H=−171 kJ/mol.   (2)In [Nasibulin et al., Carbon, 2003, 41, 2711], aspects of the occurrenceof this reaction was studied. As one can see from and FIG. 9(b),reaction (2) is also inhibited at temperatures higher than about 900° C.and kinetic investigations showed an appreciable reaction rates in thetemperature interval from 470 to 800° C. with a maximum rate at thetemperature of 670° C. It can be concluded that both reactions (1) and(2) occur in the same temperature range. The hypothesis about theleading role of reaction (1) in the formation of CNTs is supported bythe fact that CNTs were produced only in the presence of hydrogen. Theimportance of hydrogen can be confirmed by the calculations presented inFIG. 9(c) due to hydrogen molecule decomposition at the glowing wiretemperatures. In the figure one can see a temperature dependence ofequilibrium mol fraction of hydrogen atoms. The amount of hydrogen atomsis significant at the temperatures of the glowing iron wire (approx.1500° C.). It is known that the formed hydrogen atoms are more reactivethan the H₂ molecules. Moreover, a reaction between hydrogen atoms andcarbon monoxide2H_((g))+CO_((g))

C_((s))H₂O_((g)), □H=−585 kJ/mol   (3)has no temperature limitations at the operated experimental conditions(FIG. 9(d), i.e. this reaction prevails in the high temperature zone,where reactions (1) and (2) are inhibited. Thus, the role of hydrogen inthe presented aerosol method can be inferred as preventing the oxidationof the HWG and nanosized catalyst iron particles and also participatingin the reaction for the carbon atom release.

Example 2 Number Distributions of Length and Diameters of Single WalledCNTs Produced at Various Conditions and Using a Ceramic Reactor Tube

Carbon source: CO.

Catalyst particle source: hot wire generator.

Catalyst material: iron wire of 0.25 mm in diameter.

Operating furnace temperature: 1000, 1200, 1400° C.

Operating flow rates: hydrogen/nitrogen (7/93) inner flow of 400cm³/min;

-   -   CO outer flow: 400, 590, 765 cm³/min.

The example of the CNTs produced at 1200° C. and at equal internal H₂/N₂and external CO flow rates of 400 cm³/min is described and shown inExample 1.

Number diameter and length distributions of the produced CNTs wereobtained on the basis of high-resolution TEM images and presented inFIG. 10(a) and FIG. 10(b). The investigations of the influence of theexperimental conditions on the CNT dimensions were carried out at afixed hydrogen/nitrogen inner flow of 400 cm³/min varying the furnacetemperature from 1000 to 1200 to 1400° C. at a fixed outer CO flow rateof 400 cm³/min and varying the outer CO flow rate from 400 to 590 to 765cm³/min at a fixed furnace temperature of 1200° C.

FIG. 10(a) shows number length distributions of the produced CNTs. Thegeometric mean length of CNTs varies from 46 to 54 nm (with thegeometric standard deviation between 1.17 and 1.26) with the temperatureincrease in the system from 1000 to 1400° C. Increasing the CO flow ratefrom 400 to 765 cm³/min (or decreasing the residence time) leads to adecrease in the length of CNTs from 54 to 45 nm (with the geometricstandard deviation between 1.21 and 1.22).

FIG. 10(b) shows number diameter distributions of the produced CNTs. Thegeometric mean diameter of CNTs varies from 0.84 to 1.27 nm (with thegeometric standard deviation between 1.24 and 1.40) with the temperatureincrease in the system from 1000 to 1400° C. Increasing the CO flow ratefrom 400 to 765 cm³/min (or decreasing the residence time) leads to adecrease in the length of CNTs from 1.12 to 1.15 nm (with the geometricstandard deviation between 1.28 and 1.19).

FIG. 10(c) and FIG. 10(d) show the correlation between diameters ofcatalyst particles and produced CNTs at different temperatures andresidence times (CO flow rates) in the reactor. It can be seen form FIG.10(c) that the diameters of CNTs and catalyst particles initiated theirgrowth are correlated and have similar temperature dependence. Thelength of CNTs can be controlled by the outer CO flow rate, whichdefines the residence time in the reactor (FIG. 10(d). As one can seethe dimensions of CNTs such as diameters and lengths can be adjusted byvarying the experimental conditions mainly temperature and residencetime.

Example 3 Single Walled CNT Synthesis from Carbon Monoxide as CarbonSource Using Iron as Catalyst Material and Using a Stainless SteelReactor Tube

Reactor tube: stainless steel with a composition of Fe 53, Ni 20, Cr 25,Mn 1.6, Si, C 0.05 weight %.

Carbon source: CO.

Catalyst particle source: hot wire generator.

Catalyst material: iron wire of 0.25 mm in diameter.

Set furnace temperature: 900° C., corresponding to maximum furnacetemperature of around t_(max)=1070° C.

Operating flow rates: CO outer flow of 400 cm³/min and hydrogen/nitrogen(7/93) inner flow of 400 cm³/min.

This example, illustrating the synthesis of single walled CNTs, wascarried out in the embodiment of the invention shown in FIG. 3(b),wherein the reactor tube was made of stainless steel so as to providesaturated wall conditions for the iron vapor. FIG. 11 demonstrates theproduct formed at the given operating conditions. The product consistsof bundles of single walled CNTs.

Example 4 Single Walled CNT Synthesis from Carbon Monoxide andOctanol/Thiophene Mixture as Carbon Sources and Reagents and Nickel asCatalyst Material and Using a Ceramic Reactor Tube

Carbon source: CO, octanol and thiophene.

Reagent: thiophene (0.5 weight %) and octanol.

Catalyst particle source: hot wire generator.

Catalyst material: nickel wire of 0.25 mm in diameter.

Operating furnace temperature: 1200° C.

Operating flow rates: CO flow of 400 cm³/min and hydrogen/nitrogen(7/93) flow of 400 cm³/min.

Operating octanol and thiophene vapor pressure in the CNT reactor of 3.4Pa and 30 Pa.

This example, illustrating the synthesis of single walled CNTs, wascarried out in the embodiment of the invention shown in FIG. 3(a). Amixture of thiophene (0.5 weight %) and octanol was placed in asaturator (6) and was bubbled at room temperature with carbon monoxide,which was supplied from gas cylinder (1). A ceramic tube, with aninternal diameter of 22 mm inserted inside the 40-cm length furnace(Entech, Sweden) was used as a CNT reactor. Pre-made catalyst particleswere produced in a HWG separated in space from the CNT reactor. The HWG,which was a resistively heated thin nickel wire, was located inside aglass bulb. Nickel particles produced by HWG were carried into the CNTreactor with nitrogen/hydrogen (with mol component ratio of 93.0/7.0)form gas cylinder (2) shown in FIG. 3(a). In order to suppress thenickel particle evaporation inside the reactor, the walls of the reactortube were saturated with nickel by blowing nickel acetylacetonate vaporthrough the heated up to about 700° C. reactor.

In the CNT reactor, the flow carrying the catalyst particles was mixedwith the CO flow containing vapors of thiophene and octanol. Inside theCNT reactor, thiophene and octanol decomposition and COdisproportionation took place. It is worth noting that octanol vaporplays two important roles in the CNT reactor: it serves as a carbonsource for CNT formation and as a reagent for CNT purification. Formedradicals and fragments containing oxygen after octanol decomposition caneasily react with amorphous carbon deposited on the surface of formingCNTs and thus purifies them. Similarly, thiophene was utilized as carbonsource and as a reagent. Thiophene supplies sulfur to the catalystparticles. One of the roles of sulfur in the processes of CNT formationis to lower the melting temperature of catalyst particles. FIG. 12demonstrates the product formed at the given operating conditions. CNTsare single walled.

Example 5 Single Walled CNT Synthesis from Ethanol as Carbon Source andReagent and Using Iron as Catalyst Material and Using a Ceramic ReactorTube

Carbon source: ethanol.

Reagent: ethanol.

Catalyst particle source: hot wire generator.

Catalyst material: iron wire of 0.25 mm in diameter.

Operating furnace temperature: 1200° C.

Operating flow rates: hydrogen/nitrogen (7/93) inner flow of 400 cm³/minand nitrogen outer flow of 400 cm³/min.

Operating ethanol vapor pressure in the CNT reactor of 213 Pa.

This example, illustrating the synthesis of single walled CNTs, wascarried out in the embodiment of the invention shown in FIG. 3(b).Ethanol was placed in a saturator (6) and was bubbled at roomtemperature with nitrogen, which was supplied from gas cylinder (1). Theembodiment consisted of a HWG smoothly integrated with a heated verticaltubular CNT reactor. A ceramic tube, with an internal diameter of 22 mminserted inside the 90-cm length furnace (Entech, Sweden) was used as aCNT reactor. Nitrogen was supplied from gas cylinder (1). The HWG, whichwas a resistively heated thin iron wire, was located inside the internaltube. The end of the HWG tube was placed at the location with the CNTreactor wall temperature of about 400° C. This temperature was found tobe optimal, since reduced particle growth due to the agglomeration andcoagulation, minimized particle diffusion losses on the walls andprovided a reasonable iron vapor nucleation rate.

The metal particles produced by the HWG were carried into the CNTreactor with nitrogen/hydrogen (with mol component ratio of 93.0/7.0)from gas cylinder (2) shown in FIG. 3(b). In the CNT reactor, the flowof the metal particles from the HWG was mixed with outer nitrogen flowcontaining ethanol vapor. Inside the CNT reactor ethanol decompositiontook place. It is worth noting that ethanol vapor plays two importantroles in the CNT reactor: it serves as a carbon source for CNT formationand as a reagent for CNT purification. Formed radicals and fragmentscontaining oxygen after ethanol decomposition can easily react withamorphous carbon deposited on the surface of forming CNTs and thuspurifies them. FIG. 13 demonstrates single walled CNT product formed atthe given operating conditions. One can see the surface of the producedCNTs does not contain amorphous carbon precipitation and is very clean.Also it is worth noting that virtually all catalyst particles initiatedthe growth of CNTs. FIG. 13 also shows a high-resolution TEM image andthe corresponding electron diffraction pattern from a separated SWCNT of1.6 nm in diameter. One can see from the electron diffraction patternthat the CNT is well crystalline. The radii of the inner and outercircles are consistent with the length of the diffraction vectors ofgraphite 1010, and 1120, respectively. Two sets of spots in thediffraction patterns showing that the CNT is a helical tube.

Example 6 Single Walled and Multi-Walled CNT Synthesis fromEthanol/Thiophene Mixture as Carbon Sources and Reagents and Using Ironas Catalyst Material and Using a Ceramic Reactor Tube

Carbon source: ethanol and thiophene.

Reagent: thiophene (0.5 weight %) and ethanol.

Catalyst particle source: hot wire generator.

Catalyst material: iron wire of 0.25 mm in diameter.

Operating furnace temperature: 1200° C.

Operating flow rates: nitrogen outer flow of 400 cm³/min and inner flowhydrogen/nitrogen (7/93) of 400 cm³/min.

Operating ethanol vapor pressure in the CNT reactor of 2950 Pa and 73Pa.

Operating thiophene vapor pressure in the CNT reactor of 11 and 0.3 Pa.

This example illustrates the possibility to produce both single walledCNTs and multi-walled CNTs depending on the operating conditions,namely, on the vapor pressure of carbon sources (or amount of carbon inthe system). A mixture of thiophene (0.5 weight %) and ethanol wasplaced in a saturator (6) and was bubbled at room temperature with acarrier gas with and without dilution of flow containing a carbonsource. As a result two different ethanol/thiophene vapor pressures inthe CNT reactor of 73/0.3 Pa and 2950/11 Pa were obtained. It is worthnoting that the smallest operating concentration of carbon sources ledto the formation of single walled CNTs, while higher concentration ofthe alcohol/thiophene mixture led to the production of multi-walledCNTs. FIG. 14 and FIG. 15 demonstrate the product formed at the givenoperating conditions and at different ethanol/thiophene vapor pressures.As can be seen from FIG. 14, single walled CNTs were produced at thesmaller ethanol/thiophene vapor pressures of 73 and 0.28 Pa. Increasingthe vapor pressure of the reagent and carbon source (up to 2950 and 11Pa, respectively) led to the formation of multi-walled CNTs (see FIG.15) and to the formation of amorphous carbon on the surface of theproduced CNTs.

Example 7 Fullerene Functionalized Single Walled CNT Synthesis from COas Carbon Source and Hydrogen Through a Hot Wire Generator and UsingIron as Catalyst Material and Using a Stainless Steel Reactor Tube

Reactor tube: stainless steel with a composition of Fe 53, Ni 20, Cr 25,Mn 1.6, Si, C 0.05 weight %.

Carbon source: CO.

Reagent: hydrogen through hot wire generator.

Catalyst particle source: hot wire generator.

Catalyst material: iron wire of 0.25 mm in diameter.

Operating furnace temperature: 900° C.

Operating flow rates: CO outer flow of 400 cm³/min and inner flowhydrogen of 400 cm³/min.

This example, illustrating the synthesis of fullerene functionalizedsingle walled CNTs, was carried out in the embodiment of the inventionshown in FIG. 3(b), wherein the reactor tube was made of stainless steeland pure hydrogen was used through the hot wire generator. FIG. 16demonstrates the product formed at the given operating conditions. Theproduct consists of single walled CNTs functionalized fullerenemolecules.

Example 8 Fullerene Functionalized Single Walled CNT Synthesis from COas Carbon Source and Hydrogen Through Hot Wire Generator and Water Vaporas a Reagent and Using Iron as Catalyst Material and Using a StainlessSteel Reactor Tube

Reactor tube: stainless steel with a composition of Fe 53, Ni 20, Cr 25,Mn 1.6, Si, C 0.05 weight %.

Carbon source: CO.

Reagent: water vapor at 150 ppm.

Catalyst particle source: hot wire generator.

Catalyst material: iron wire of 0.25 mm in diameter.

Operating furnace temperature: 900° C.

Operating flow rates: CO outer flow of 400 cm³/min and inner flowhydrogen/nitrogen (7/93) of 400 cm³/min.

This example, illustrating the synthesis of fullerene functionalizedsingle walled CNTs, was carried out in the embodiment of the inventionshown in FIG. 3(b), wherein water vapor was used as a reagent andintroduced via a saturator (6) and wherein the reactor tube was made ofstainless steel. FIG. 17 demonstrates the product formed at the givenoperating conditions. The product consists of single walled CNTsfunctionalized fullerene molecules.

What is claimed is:
 1. An apparatus for producing carbon nanotubes froma gas phase, comprising: a device configured to produce an aerosol ofpre-made catalyst particles by physical vapor nucleation of catalystmaterial, the aerosol of pre-made catalyst particles being formed bynucleating supersaturated vapor, wherein said device configured toproduce said aerosol of pre-made catalyst particles comprises a nozzleconfigured for adiabatic expansion; and one or more reactors forproducing carbon nanotubes using said aerosol of pre-made catalystparticles and one or more carbon sources, the one or more reactors beingconfigured for the introduction of the aerosol of pre-made catalystparticles, the introduction of the one or more carbon sources, andreacting the pre-made catalyst particles and the one or more carbonssources to produce the carbon nanotubes.
 2. The apparatus according toclaim 1, wherein the apparatus further comprises one or more of thefollowing: one or more catalyst particle classifiers; one or more carbonnanotube samplers; one or more carbon nanotube classifiers; one or moresources supplying energy to said device configured to produce saidaerosol of pre-made catalyst particles or to said reactor; one or moredevices configured for introducing one or more reagents or additives tothe device configured to produce said aerosol of pre-made catalystparticles or to the reactor; one or more aerosol samplers or classifiersextracting all or part of the carbon nanotube aerosol flow; or one ormore aerosol samplers or classifiers extracting all or part of acomposite carbon nanotube aerosol flow.
 3. The apparatus according toclaim 1, wherein a surface of at least one of the reactor or the deviceconfigured to produce said aerosol of pre-made catalyst particlescontain material included in one or more catalyst particles or in thatthe surfaces of the reactor or the device configured to produce saidaerosol of pre-made catalyst particles are saturated with materialincluded in one or more catalyst particles.
 4. The apparatus accordingto claim 1, wherein there are two or more reactors and said reactors areoperated in parallel and said parallel reactors are operated atessentially similar conditions or with essentially similar materials soas to produce carbon nanotubes with essentially similar length,diameter, morphology or chirality or said parallel reactors are operatedat different conditions or with different materials or methods so as toproduce carbon nanotubes with two or more distinct lengths, diameters,morphologies or chiralities.
 5. The apparatus according to claim 1,wherein at least one of reactor length, volume wall temperature or flowrate of carbon sources, reagents or carrier gases are configured tocontrol at least one of residence time, or temperature history ofcatalyst particles, carbon nanotubes or composite carbon nanotubes inthe reactor(s) or pre-reactor(s).
 6. The apparatus according to claim 1,wherein said device configured to produce said aerosol of pre-madecatalyst particles comprises one or more pre-reactors.
 7. The apparatusaccording to claim 1, wherein said device configured to produce saidaerosol of pre-made catalyst particles comprises a hot wire generator.